Step-by-step explanation:
cost of 1 kg of jam = x
cost of 1 kg of butter = y
3x + 2y = 29 .....1
6x + 3y = 54 .....2
.....1 × 2 both sides of equation
6x + 4y = 58 .....3
.....3 - ......2
y = 4
replace y = 4 in 1......
3x + 8 = 29
x = 7
